Interisland ocean shipper Young Brothers Ltd. said late yesterday that it has requested a 17.9 percent rate increase for all of its interisland cargo shipments, citing $90 million in investments in transportation improvements over the last three years, rising costs and reduced cargo volumes.

If approved by the state, it would be the largest rate increase in at least 13 years for the company and the fifth straight year of rate increases. The company last increased its rate in August.

Young Brothers said yesterday it requested an effective date of August 2009. The state Public Utilities Commission can take up to 45 days to review the request.

Young Brothers took $987,000, or 8.6 percent, off the increase in revenue it could have requested to reach 17.9 percent in an effort to recognize Hawaii's “;economic predicament,”; the company said.

“;Developments over the course of 2009, such as an end to the current economic slide and a rebound of cargo volumes, may decrease the amount of our requested rate increase,”; Roy Catalani, vice president for strategic planning and government affairs, said in a statement. “;Unfortunately, such a rebound is not expected by our economics expert.”;

Young Brothers will work with communities on Molokai and Lanai to limit the requested rate increase, as they do not have well-developed consolidation or on-island distribution systems, and will also collaborate with farmers to review the possibility of increasing the 30 percent discount it provides for local agricultural products.

If fuel prices remain stable through February, Young Brothers projects it will “;substantially reduce”; or even eliminate its 6.57 percent fuel price adjustment in March, the next time it is scheduled to be reviewed.